Flexible impeller pumps are often used to pump fluids. In the flexible impeller pump 10 illustrated in FIG. 1, an impellor 12 having flexible vanes 14 extending radially from a central hub is mounted for rotation within an opening of a housing 16. The impellor 12 is mounted to a shaft, which is mounted for rotation relative to the housing 16 about an axis. The opening is in fluid communication with an inlet 18 and an outlet 20. As the impellor 12 is rotated (clockwise relative to the view direction of FIG. 1), tips of the flexible vanes interface with sidewalls of the opening to draw fluid from the inlet 18 and discharge the fluid to the outlet 20. The housing includes a cam portion 22, which has a sidewall that is disposed closer to the axis than the other sidewalls of the opening, thereby causing increased bending of the flexible vanes 14 as they pass by the cam portion 22. As the impellor 12 rotates, each flexible vane 14 exits the cam portion 22 in the vicinity of the inlet 18, travels around an annular portion of the opening to the outlet 20, and then reengages the cam portion 22 to repeat the cycle. Upon exiting the cam portion 22, a flexible vane 14 straightens thereby increasing the volume bounded between the flexible vane 14 and the adjacent trailing flexible vane so as to draw fluid from the inlet 18 into the space between the flexible vane and the adjacent trailing flexible vane. The fluid in the space is then propelled around the opening to the outlet 20 by the impellor vanes. At the outlet 20, the flexible vane reengages the cam portion 22 and is cause to undergo increased bending, thereby decreasing the volume bounded between the vane and the adjacent trailing vane so as to discharge fluid from the space to the outlet 20. A suction created by the straightening of the vanes upon leaving the cam portion enables self priming of the pump 10 by allowing atmospheric pressure to push the liquid into the pump 10.
Existing flexible impeller pumps, however, suffer from a variety of common problems. For example, as illustrated in FIG. 2, the repetitive bending of the flexible vanes can lead to fracture of the vanes and/or permanent bowing of the vanes. The sliding of the tips of the flexible vanes along the sidewalls of the housing, especially along the sidewall of the cam portion, can lead to localized wearing, pitting, and/or ripping of the tips of the flexible vanes.
In addition, relative motion between the end faces of the impellor and adjacent end walls of the housing can result in additional wear damage to the housing end walls. Wear to the housing end walls can be especially significant where the flexible impeller pump is used to transfer abrasive fluids. For example, as a non-limiting example, many dispensable edible fluids contain particulate, some of which are abrasive. And many food dispensing pumps have plastic housings. The plastic end walls of such pump housings can experience significant amounts of wear due to the presence of such abrasive components.
Thus, there is believed to be a need for improved flexible impeller pumps, particularly flexible impeller pumps suitable for use with abrasive fluids, such as dispensable foods having abrasive components.